Variable pitch propeller



Dec. 17, 1946.

- o o o -o o o o R. STEVENSON VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 15 Sheets-Sheet 1 ATTORNEYS.

Dec. 17, 1 946. STEVENSON 2,412,923

VARIABLE PITCH PROPELLER A TTORNEYS.

Dec. 17, 1946. R, S EVENSON 2,412,923

VARIABLE P I TCH PROPELLER Filed Sept. 6, 1940 15 Sheets-Sheet 3 k V INVENTOR. 790,6 1? Jkr plmsaza N mm A TTORNEYS.

Dec. 17, 1946. 1 R. S I'EVENSON 1 9 VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 15 Sheets-Sheet 4 INVENTOR. flab/e f2 67 ray/rs 0/2 By flaw, W144,

A TTORNEYS.

Dec. 17, 1946. R. STEVENSON 72,412,923

VARIABLE PITCH PROPELLER Filed Sept.' 6, 1940 15 Sheets-Sheet 5 INVEN TOR. gaerf :i/e 1 9/760/2 l A TTORNEYS.

Dec. 17, 1946. R, STEVENSON 2,412,923

y VARIABLE BITCH PROPELLER Filed Sept; 6, 1940 15 Sheets-Sheet e INVENTOR. eoerfcffi V/I-SOl? fizz/l 1m w n 4,

A TTORNEYS.

Dec. 17, 1946. i R. STEVENSON VARIABLE PITCH PROPELLER Filed Sept. .6, 1940 13 Sheets-Sheet 7 A TTORNEYS.

Dec. 17, 1946. STEVENSON V 2,412,923

VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 .13 Sheets-Sheet '8 INVENZOR.

age/3X dfrexiwoxz flMu/mw A TTORNEYS.

Dec. 17, 1946.

R. STEVENSON VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 15- Sheets-Sheet 9 A TTORNEYS.

Dec. 17, 1946.

R. STEVENSON VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 v lllll'l llll Riszkvouz ATTORNEYS.

Dec. 17, 1946. j R. STEVENSON 1 23 VARIABLE PITCH PROPELLER 7 Filed Sept. 6, 1940 15 Sheets-Sheet l2 INVENTDR. oerzf/evensaxz 1 A TTORNEYS.

Dec. 17, 1946. R STEVENSON 2,412,923

. VARIABLE PITCH PROPELLER Filed Sept. 6, 1940 l5 Sheets-Sheet 15 Resmvom IN V EN TOR.

A TTORNEYS.

Patented Dec. 17, 1946 VARIABLE PITCH PROPELLER Robert Stevenson, Providence, R. I., assignor to Stevenson Engineering Corporation, a corporation of Rhode Island Application September 6, 1940, Serial N0. 355,626

Claims. 1

This invention relates to aerial propulsion, more particularly to a mechanism for changing the pitch of the blades of a propeller. It has for its pbjects various accomplishments in the improvement of such mechanism. One of the objects of the invention is to provide a hollow shaft in connection with a mechanism for varying the pitch of the propeller blades in order that a shot may be fired through the shaft.

Another object of the invention is to provide a self -locking arrangement in connection with the varying of the pitch of the blades of the propeller so that there will be a sufficient resistance to pressure on the blades to maintain them in adjusted position which under some conditions such as due to diving or failure of oil pressure causes the blades to move from adjustment and flatten out. Another object of the invention is to provide for a large portion of the operating mechanism, such, for instance, as the pumps and governors to beat a location inboard from the plane of rotation of the propeller blades that the operating mechanism may be better supported.

Another object of the invention is to improve the root mounting of the propeller blade in the hub of the propeller and to enable more blades to be mounted on a hub of a given size.

Another object of the invention is to arrange an operating hydraulic power mechanism for the changing of the pitch of the propeller blades which will have large areas that lower pressures may be utilized of the hydraulic means to develop the power necessary for shifting the pitch of the propeller.

Another object of the invention is to provide an automatic control by means of a governor for the fluid pressure control of the blade mechanism.

With these and other objects in view, the invention consists of certain novel features of construction, as will be more fully described, and particularly pointed out in the appended claims.

In the accompanying drawings:

Fig. 1 is a sectional view taken generally centrally and illustrating various parts of the outboard propeller shaft .and certain of the controls for the varying of the pitch of the propeller blades;

Fig. 2 is a section on substantially line 2-2 of Fig. 1;

Fig. 3 is a section similar to Fig. 1 taken on a different plane than Fig. 1 and on a larger scale showing certain parts of the operating mechanism, the section being substantially on line 3-3 of Fig.

Fig. 4 is a section similar to Fig. 3 but showing the more outboard portion of the mechanism and also on the same scale as Fig. 3 and larger than the scale of Fig. 1;

Fig. 4a is a central longitudinal sectional view of an alternative form of mechanism to that shownin Fig. 4;

Fig. 5 is a sectional view similar to Fig. 4 but showing a diiferent plane of section through the propeller shaft;

Fig. 5a is a sectional view taken substantially on line 5a-5a of Fig. 4a;

Fig. 6 is a section taken substantially on line 6-6 of Fig. 4;

Fig. 6a is a sectional view taken substantially on line Sa-Ea of Fig. 4a;

Fig. 7 is a section on line 'l'! of Fig. 6;

Fig. 8 is a section on line 8-8 of Fig. 6;

Fig. 9 is a section taken substantially on line 9 9 of Fig. 3;

Fig. 10 is a section on substantially line l0l0 of Fig. 1;

Fig. 11 is a detailed view of the pump assembly;

Fig. 12 is a section on line l2l2 of Fig. 11;

Fig. 13 is a section on line ill-I3 of Fig. 11;

Fig. 14 is a section on line "-44 of Fig. 11;

Fig. 15 is a schematic diagram illustrating the relationship of the pumps, control valves and conduits in connection with the reservoir;

Fig. 16 is a detail sectional view illustrating certain of the manual control valves and taken on line ilk-l6 of Fig. 18;

Fig. 17 is a section on line l'l-l'l of Fig. 16;

Fig. 18 is a sectional view taken at right angles to the showing of Fig. 16 and taken through the center control valve;

Fig. 19 is a fragmental section showing certain fluid conduits on substantially line l9l9 of Fig. 10;

Fig. 20 is a section on line 2020 of Fig. 19;

Fig. 21 is a section on line 2l2| of Fig. 19;

Fig. 22 is a section on line 22--22 of Fig. 19;

Fig. 23 is a schematic view illustrating the control conduits with relation to the various valves, governor, pumps and power mechanism, also showing the electrical control for the motor pump.

In the use of an air propulsion mechanism the change of pitch of the blades for the purpose of changing the effective drive of the propeller and for feathering the blades of the propeller to lessen the resistance when the engine is stopped in the air or for unfeathering the blades when the engine is idling on the ground, strong pressures are developed which it is required to overcome. There is also the problem of shooting with 3 feathering blade propellers which cannot be done through the blade at the present time as it is not so arranged that shooting may be done through the shaft of the propeller, as this shaft has been utilized for other purposes. To overcome these disadvantages I have arranged that shooting may be done h i sh the. s af urth r div n Of. a plane,thou'sands of pounds p'er square inch or pressure is 'd'evelopedbnthe propellerblade's" and in propellers Whose pitch is changed there is fre quently. such pressures developed that the resistance to turning is overcome and the bladdflatten out because of such pressures as are developed. Accordingly, it is desirable thatfseme arrange; ment be made so that propellers cannot flatten out and that their driving force may still continue to operate. Accordingly, I have arrangedfor a locking device so that the propeller cannot flatten out, and I have provided a controlled positive actuating mechanism for returning the propellers to their "feathering position. This mech shear whiehI have developed is" a completely s'elf contained 'unitwhich may be'applied'to the propeller shaft and itself containing all of the liquid used for the hydraulic power, notutilizing the lubricating oil 'of the" engine which would be entirely separate therefrom. The'mechanism is also "arranged so thatit' will operate in the powe'r tra'nsrnitting" fluid that the working parts may be continuously lubricated Theappaiatus" may beco'n'sidered as a plurality of assembled cooperating units which acttoget-her; 'T-he're is a propeller'blademounting assembly, a pitch-changing mechanism forthe propeller'blades; a fluid pressure'supply'consisting of a pump whichis locatedatsome convenient point, usually inboard cf thepla'r'ie o'frotation of the propeller blade," but preferably close to the pitchchanging mechanism, andamea'ns for control ling the pressure supply of the fluid for thehydrauli'c powerirom the pump 'to the pitch-changing mechanism. These various parts of the mechanism: will} be described substantially in the orderemr'ated.

q z l e' blede mealt me It will be understood that I have illustrated merely" the s atement portion of theprqpeller shaft 25 whi'chfe5it'ends outward through the casing" 26' supported by a radial ball bearing 21' nihuhted ir'fthe casing, and dry from: spine suitable driving mechanism such, for instance, as an ngi 'lef A propeller hub}? is mounted on the pl'opeller 'sha'i'tjzs' of splines 23 at a plu'rality" of difierent location's peripherally about the shaft, as shown in' Fig' 2 Thisjhu'bZB', a'ssh'ownf in Fig) zifis arranged for the mounting of four propeller blade'sfthe same being equally spaced at an arcuate distance of ninety degrees; and for this; purpose there are four outwardlyprojec'ting'portions 3'0 from'th'e' hub 28, each arranged tOpirovide' anintegralstud 3i and a collar 32"spacedlfrom 'the stud; "This stud 31 is tapered asat 33 atitisinner end, anda gear 341s mouhteiiupon this stud having a long tubular bearing porti'olf35 fiared as at 3 6-to receive the tapered portion 33': of the stud. This tubular bearing is flanged inwardly as at 31,- one end'to house a thrust ballbearing'SS therein, the inwardly-extending, portion also 'receiving the reduced portin 39;;of. the stud..3l which is threaded as at 4B and provided Witha nut 41 to rotatably mount the same onthestud.

. A flange, 4 5. extends lat'erallyfromthe tubular bearir gQpOrtiOl' 35.Which assists in locating the cup 46 which has an openin 41 to receive the tube 35. The cup is threaded as at 48 to receive the threaded root 49 of the propeller blade 50 and after being assembled therewith is keyed to the cup by dowel pin 50 which projects from-the inner side of the cup to be positioned into recesses n the flan e. it This, can. is re i l l "with a roller bearin surface 5.! against which the rollers 52 engagepn one side while engaging thecircular plate on the opposite side which is held in position by the nut 54 threaded as at 55 to engage the outer threads 56 of the projecting portion 32. In

this way the cup 45 is rotatably mounted on the projection "Sill and provided with roller bearings to support the centrifugal force tending to throw the blade outwardly so that easier rotation of the blade for changing its pitch may be had.

Each gear 34 is in the form of a worm gear and is rotated by a worm 51 which has portions 58 and 58' extending therefrom and in which a bore 42. extends therethrough. Each blade liot is of the same construction, ahdth'fdur-Worni sj 5T areoperated in unison to actuate the s ame; Thus, all of the blades will rotate about their studs 3i simultaneously to receive thesame feathering orangular position with relation thereto. Each of the worm gears 34 is of mental shape and is limited in its rotating move' ment by suitable abutment means as 59 engaging the ends of the segment. As this root mounting is "located within theoil casing, it is continually operating in "a lubricant.- Each worm 51 1s of the type more'fully describedin my-PatentNo. 1,982,768 which will not be rotated bytorque ,ex; erted onthe blade.

B qdrrit h; cha g ng: mechan m In order to rotate the worm 51 to change the pitch of the blades 50-, each worm 5-!- is pfvided with a gear 15 (see Fig. 3; on an extendin per tion 58 which meshes with the internafteeth 16 (Fig. 1-) of; the ring gear '11; which i fixed tfothei casing l8- '(see Fig. 4) of the actuating druin havk ing fins i is for. strengthening the sazii'ejf This drum is fOrmed-pf halves' bolt ed together as at 89 (Fig 6) and holding between the seiihsgso se-i curedtogether vanesfl l having a' packing portion 32 held between; the sections" as rid tdfbf the vanes by means of-rivets8'5l. End plates 86 (Fig. ll for; the drumar'e 'rotatably'mountedtherein by means of. ball bearing members 87 and packing rings at are relatively rotatably mountedbet ween the casing'l8- and the end plates 86- by means of tongues '89- (Figs; "'idc'at'd iii grooves 90 in the drum 1:; and in the e'hdpiats 8'6 and- 86!. providing a seatat these relatifv ta'table connections, "Ifhe'se emanates 86 g 4). and 86 are each p rovi'ded with inwardly 'eic tending hubs 9i which are splined as'at 9-2 onto the shaft extensions 93- provided with a 9 4. bolted as at 95 to the hub 28 of the propeller"; thesehubs' interlocking with one women's; at 96, the hubs beingheld togetherfby means ofjthe nut 9Thavingthradedengagement as at- 98 witl the-shaft 9 3and locked inposition by the then; nut- 99s A paclging l0 prevents leakage." Radial fin'sml (Fig, 6) consisting of sections I025 and l03 are located in a recess I04 inthe hubsjl arid are connectedto the" end plates 85 byineansi t rods I05. Packing members |06 are held between the' sections 162 andTpIi -by means" of the r ,ets W T- and. are cast integral:with'thepackingri 88} Suitable inlet parts HJS andIUQ arepro m thevanes HM for trans m'issio rl of} the fluidj which is to supply the force for relativelyrotating the vanes IDI and SI with reference to each other. These inlet ports I08 and I09 extend into circular grooves IBM and Ill9a respectively, and which grooves receive fluid through communicating passages to be hereinafter described.

Alternatively, the gears 'I5may be driven as illustrated in Figs. 4a, 5a and 6a, in which case these gears engage with the internal teeth IIO of the gear III which is also provided with a hub gear II2, which hub rotates upon the casing H3.

This casing I I3 is shaped to provide a cylinder H4 in which a piston I I5 operates. which piston is provided with four threaded ape'rtured bosses I I5a; each adapted to threadedly receive a threaded shaft. I H. The threads I I 8 on the shafts I I1 are of such long pitch that thepiston I I5 may be moved to cause rotation of the shafts. Each of these shafts is equipped with a gear II9 which meshes" with the teeth of the gear I I2 so that upon operation of the shafts i i! the ring gear II I will be "rotated toin turn rotate each of the gears I5. The shafts I H are each suitably supported at one end by thrust ball bearings I properly secured in bosses I2! provided in the closure cap I I ia of the cylinder, while at the opposite end portion of each shaft In a suitable packing I22 and annularmember I23 form a seal for the shaft which protrudes from the cylinder that the operating fluid will not escape. If it is desired to drivethe shaft, liquid will enter through the conduit :24 d

to drive the piston inboard, while if'it is desired that the piston be driven outboard, the liquid will be caused to enter through the conduit I24a. The

conduits for the supply of fluid are formed in the forward portionof the shaft,as illustrated in Figs. 5a and 6a. Annular packing members H517 and H50 are properly securedto the piston H5 The pump There are three pumps utilized in this apparatus, each of which performs the function of developing the required amount of fluid pressure for operation of certain mechanism in response to controls for shifting the propeller blades angularly. These pumps are suitably located, usulally close to the mechanism which they are to operate that the control lines may be oi short extent. The drive for the mechanically driven pumps is taken from the internal toothed ring gear I25 (see Fig. 3) which is suitablyfastened by means of a web I 28 to the hub of the propeller shaft and serves to drive a gear I21 (see also Fig. 10 to Fig. 11 for the continuation of the de- 'scription.

The pump proper is secured, to a fixed part of the. apparatus which provides a boss I3I extending radially of the drive shaft. Assembled on this boss there area plurality of sections I32,

I33 I34, I35, I36 held to the boss by bolts I54 extending through all of the sections and section I36 held to section I36 by bolt I36". The boss I3I is recessed as at I3! so as to receive the portion I38 of the section I32 which is provided with a bearing bushing I39 for the reception of the shaft I30. This shaft is provided with a flange I33-having sealing engagement with the bush- 1 3. I .d. sh i u en a ment by sp in -l lfmlee ig flea-reg es .igthe shart lanandrenr gaging ball 300". The section I33 and the section I are each provided with'a central opening I40 in which one element IIII of thepump is rotatably mounted, while I the other element I 42 ofthe pumpis keyedto the shaft I30 so that upon rotation thefluid in the space I43;wi11 be pinched ahead of the rotor from one side to the other, that thefluid maybe pumped, as is. a known pump function, The other sections are provided with suitable channels for the conduction of. the fluid fromthe reservoir to thernech;

.anism which it is to operate. The reservoiris in the bullet-shaped end and consists of the space remaining in the casing 145 surrounding the blade-actuating mechanism. This reservoir is connected to the annular space I46 through conduit I 4I (seeFig. 3), conduit I48, I49 connecting with said reservoir. Conduit I48 is formed by tube I59 having outward projections I52 to engage the inner surface of the shaft 25 and provide aplurality of channels of a necessary num ber for the conduction of fluid therealong. The channel I48a provides a passage for thefiuid to openings 65 and 66 (see Fig. 9) which open into the circular groove I 09a, and the channel I481) provides a passage forthe fluid to openings B! and 68 which lead into the circular groove III8a, The annular space I is connected to the aligned openings forming a conduit I53 extending along the length of the pump as shown in Fig ll. The

line of fluid flow by reason of the pump maybe traced from theintake side of the pump from conduit I53 through Opening I55, thence passage I55 intothe interior I43-of the uppenpumD. 1o- .tor. The discharge of this pump is through passages I5'I, I58, I59 and thence to recess I60 (see Fig. 12) and outwardly throughrecess I10 and pipe I'II.'. If the pressure buildst-up. too high in this pipe, the .recess I60. will then discharge through the ball Ifil backedup by Spring I62 and controlled as to tension by threadedrplug I63. The .fiuid from the chamber IBLpasses through the conduit I65 back to the conduit .I53 connected to the reservoir. The intakefof the lower pump is through opening I33, IE! to. the pump interior I43 and from the pump into the space I68 which is of; arcuate shape and thence throughconduit I69 to the outlet line. I'IIia and I'IIa. This'lower pumpispprovidedwith, a re-- lief valve similar tothat of the upper pumpand the supporting structure and has secured on this gbossa series of sections I86, I81, I88, I89,; and .a motor mounting plate I90. wThese sections are suitably bound in position. by bolts (not shown) such as described in connection with'the pump shown in Fig. 11. Through all of these sections there extends drive shaft I9I which hasimount ed upon it the impeller I92 surrounded by, the portion I93, each corresponding to the parts I42,

I II shown in Fig.- 14. This pump connects with the reservoir by the conduit I94. A suitable electric motor is mounted and properly secured .on the plate and when energized,;the shait. I9.I will be driven to actuate the motor pump. I i3 7 The controlm'eans the blade has arrived at a certain position so as tohold the same-there, and an automaticallyope'rated governor whichcauses'abalance and controls the pump action in its supply of pressure tothe actuating drum; These units will now be-described. r i

I The manual control valve (seeF-igs. 16-1-8) consists-of a'bodyportion 225- suitably mounted upon a base 226- which in turn is secured to some suitable'support 228 in the cockpit orcontrol room handy for the operation by the pilot. The body 225 has a series of bores 229, 236 and 25 The governor Referring to Fig, 10, a boss 29f provided one fixed portion of the mechanism is provided: with a bore 255! in which there is rotatably mounted a shaft 292 provided-with a gear 293 at its inner end driven by a gear 294. suitably secured on the, end-of a short shaft 294a on which a gear 29417 is mounted and which meshes with the teeth of the gear I28 which is; connected to and driven by the hub of the propeller. The shaft isrotatably mounted in ball bearings 295 held in accordance with the number of valves which I are to be provided. In this case there are three, one for the usual driving range of the pitch of theprop'ellen one for feathering, and the other for unfeathering of the propeller blade. Each bore is provided with a pair of conduits as 232 and233 for the bore 229'; 234 and 235 for the bore 230; and 236 and 231 for the bore 23; each of which is generally L-shaped asillustrated in Fig.1; whileeach bore is-also provided with a pair-0f conduits, as at 2310.,238, 239; 243, 24!, 2;- Ineachborethereis a plunger as at 243,

244i and 24fi and eachplunger'is provided with openings. or channels 'a s-at 246 241, 248, 239; 250; 251 for-alignment with the aligned channels perpendicular to the axis of each. of the bores when the plunger is in one position but. out of such alignment when the'plunger is in a different position. Each of these plungers is forced' upwardly by springs 252, 2515,25 3 seated, in suitable recesses in the base and in each plunger. Plungers are also reduced to provide a neck portion 255, 256, 257 which extends through a top plate 258 having openings. suitably aligned with the axial bore in the body:

A series of collars i259- extend about. each'of ithe openings in the top plate,

I and'a packing gland nut- 26B is threadedinto such collar so as to provide afiuid-'tig-ht fit about the. plunger.

The. topplateiisaiso provided with a bossloc atedopposite to each plunger, as at" 2'6! (see Fig. 18), which provides a pivot at 262 for a handle or lever, there being one for eachiplungeri' designated 263, 2631; 2&3", each having; a rounded projection zen toveng'age the top of the neck 255 of'e achplungler-so that when the lever is depressed, the plunger will be forced inwardly to cause its opening to connect with heldtin engagement with theportion of its wall in'whi'ch the openings-0r coriduitssoccur byreason of set screws-2169. v r. f I

by a cap 295; within the casing 293,, and suitably mounted by pivot 298 on this shaft 292 are a pair of governor arms 299 having weights. 300' on the endsthereof. Portion 39.1 of these: arms engages a plunger 392 in the bore 3930f this shaft292 so as to-force thesame inwardly toward the shaft as the arms are thrown to theirouters most position, as shown in Fig. 10. When the plunger is in. its innermost position, as shown in Fig. 10, one-set of openings permits communication, while, when in its different positions, a different set, of openings operates. Pressures will be effective to move the plunger 392 outwardly when the arms drop. The plunger is provided with a hollow portion as at 394 and communi cates with the conduit 39.5 which connects with the reservoir annulus I45. Suitable openings 3 06 and 3,9? are provided from this hollow center portion to register with openings 358; and 3,09 in the shaft which connects with annular grooves 315 ands from which suitable conduits lead through the boss 29!). i I T -au o t v i n ed enera ly 25 is housed in a bo-ssalso extending outwardly from the fixed portion of the machine as showndn FigmlO, which boss forms the outer casing. of the valve having a. bore 326- in which there is i the plunger type valve 321 having a valve seat 328 to engage the plunger portion 32s when seated.

Fluid enters through the opening 330 above the valve and opposite a recess. in the valve and will be discharged through the valve seat and outwardly at 331 when the valve is open, as shown in Fig; 10. The valve is slidably guided: in the bore 332 of the plug 333 and forced in one direction by spring, 334'. This valve has a rounded end 335'which rideson a fin 336 of a'plunger s37 which is suitably guided for axial movement by other fins 338" and is'forced in one direction by a spring 339-(see Fig. 3) having a plug 340 tohold it in, adjusted position. This plunger is provided with a stem 34'! which is secured to the raceway of ball bearing member 3,42, the opposite raceway being'connected to the threaded shaft 344 which is splined to, axially slide with reference to the worm; 51.; Thus, as the propeller blade turns, the plunger 34! is forced to the right as shown in Fig. 3 against the, action of the spring 339 so as to permit the valve to close and shut off the conduits throughwhich fluid flows for-control of or providing pressure for returning of the blade when it reaches its flying pitch of forty-five degrees.

A similar arrangement for movin another plunger 366 to actuate the helically=slotted drum '36l is provided so that an indicatorOperated through mi-tregears 36% and 363' on shaft 364 maybeactuated; i

. Ocem For a better understanding of; theoperation of this mechanism, reference is made to Fig. 23

shows diagrammatically the several clentrel mechanisms, pumps and valves for control ling the flowlof fluid through these several devices'i' 'Theffluid from] the pumps flows through proper conduits to the manually controlled valves and from there through proper conduits enters the channels I48," l48a andl49a through openings 69, 1D and -'H (Fig. 19) provided in the section 12 of the propeller hub. The governor is in: terposed in thepassages extendingfrom'the manually controlled valves and in which the fluid from the upper and lower pump flows. 5

Let "it be assumed thatthe motive force has been-set intomotion and'the several parts properly adjusted which will cause the propeller hubs and parts secured thereto'to revolve with the shaft 25 as a unit and with the propeller blades set at an idling position. Shaft-34! (Fig. 3) will be i a forward position (to left Figs) an valve 6l (Fig. 23 or 321 Fig. 3) will be open. The operator then actuates manually the lever 2630f the control mechanism; generally designated 225 in Fig. 16, and forces the valve plunger 243 downwardly against the pressure of the spring 252 until the latch 265 engages the portion 286 provided on the lever and locks this lever in position,lwhich aligns the conduit 243 with the conduit 232 and 23111, and the conduit 24! with the conduits 233 and 238. The fluid will then flow (Fig. 23) from the upper pump, here designated 60, through the conduit 403, through the' aligned conduits 233, 241 and 238, through the conduit 4!, through conduit 432, through the valve 5|, which at the present instant is open to the flow of fluid, through conduit 403' which branches into c0nduits=404 and 405; which open intothe clylinder provided inthe casing I8; The fluid from the lower pump, designated 63, flows through 405,aligned openings 232, 243 and me, through conduit'4l'll, and through conduit 409 and into the cylinder through branch conduits4l0and4ll.

Under normal operating conditions pumps 63 and 63 apply pressure to opposite sides of the fluid motor to lock the fluid motor. The governor valve 62 vents or by-passes the fluid from either pump so that the normal pressure of the other pump will operate the fluid motor to vary the pitch, it being apparent that the pressure on one side of the vanes decreases through the operation of the governor so that the pressure on the other side will vary the angularity of the propeller blades. The pressure built up on one side of the vanes 8! will cause a relative movement of the casing 18 and the vanes Hll which are secured to rotate as a unit with shaft 25 and will rotate the gear I6 which is fixed therewith to cause a rotation of the Worm screw 51 and rotate the propeller blades to an advanced position.

If the pitch is varied beyond the normal operating range the valve 6| will close and render the governor control of the pitch motor inoperative. This valve 6| is controlled by the plunger 33'! which is operated by the rotation of the worm screw 51. This plunger will move to allow the valve member 329 to be seated against the valve seat 328 to stop the passage of fluid through the valve.

If it is desired to feather the propeller blades, the fluid power is controlled for this purpose. The lever 263 is moved to release the plunger which is moved upwardly by the spring 252, and the lever 263' is then moved to force the plunger 244 downwardly to align the openings 234, 243, 239 andthe openings 335, 249 and 246 with each other. In moving the lever 263' the electrical switch 26'! will be actuated to close the electric 10 motor circ'uit- 4-l2 which will; cause'the' motor pump generally design'ated64, to bepla'ced' in operation, and the fluid will flow therefrom through conduit 4I3, thence through aligned openings 234, 248, 239, thence through conduit 4| 4 which connects to conduit 4G3, and thence through conduits 404 and 405 to the cyIinderTB' to actuate the vanes to move the propeller blades to featherposition. F If it is desired to return th bladesto unfeathered position, other levers are allowed toreturn to normal, and the lever 263" is moved in'a direction to forcethe plunger 245 to alig'n the o-penings236, 253 and 24! and openings 231,25} and 242 which will permit the flow of fluid from the pump 64 to conduits 4 l 3, thence through con duit' 496 through conduit 236, then through aligned openings 236, 250 and 24'l,'thence through conduit 4!! which communicates withconduit 4l0'and'4l l', and from there into cylinder l8' '-to move the vane'saffectedther'ebyina directionto unfeather the propeller blades. The fluid on the opposite side of "these vanesishreturned'to the reservoir I 46 through conduits 404'and 405, thence through aligned openings 242, 25l,.231 andc'onduit 418 which leads intothereservoirfthe switch 261 affected by the' moving of the lever 253' having previously set themotor pump intoaction. 1

i The" return flow of fluid when the. plunger 244 is in a position to align the several openings therein may be traced through thelconduits 4H! and 4lland conduit 4l8,fithence' through aligned openings 240,249,235 and conduit M9 which also leads to the reservoir I46. i f i T Iclaim: Y l l. A variable pitch propeller mechanism comprising a shaft, a'propeller hubmounted. on said shaft and rotatbletherewith, a=plurality of propeller blades each rotatably anchored to said hub for angular movement about their respective axes, a plurality of threaded shafts, a gear train operatively connecting said threaded shafts to said propeller blades for rotating the same about their respective axes upon rotation of said threaded shafts about their respective axes, said gear train including a ring gear embracing said shaft, and pinion gears carried by said threaded shafts and in engagement with said ring gear, pinions engaging said ring gear and connected to said blades, a cylinder, a piston slidably movable therein having a plurality of threaded openings extending therethrough, said threaded shafts extending through said openings and in threaded engagement therewith and rotatable about their respective axes in response to movement of said piston.

2. A variable pitch propeller mechanism comprising a shaft, a propeller hub mounted on said shaft and rotatable therewith, a plurality of propeller blades each rotatably anchored to said hub for angular movement about their respective axes, a plurality of threaded shafts, a gear train operatively connecting said threaded shafts to said propeller blades for rotating the same about their respective axes upon rotation of said threaded shafts about their respective axes, said gear train including a ring gear embracing said shaft and pinion gears carried by said threaded shafts and in engagement with said ring gear, plnions engaging said ring gear and connected to said blades, a cylinder embracing said shaft, a piston movable in said cylinder having a plurality of threaded openings therethrough, said threaded shafts extending through said threaded openings and in threaded engagement therewith and rotatable about their respective axes in'response to movement of said piston. Y

3, A variable pitch propeller mechanism comprising in combination with a hollow shaft opened at each end thereof and free of any obstruction therein and a propeller hub mounted on said shaft and rotatable therewith, a plurality of propeller blades each rotatably anchored to said hub for angular movement about their respective axes, a cylinder in the form of an annulus embracing said hollowshaft intermediate the ends thereof a piston having a plurality of threaded openings therein movable in said cylinder, and threaded shafts extending through said openings and in threaded engagement therewith and rotatable about their respective axes in response to movement of said piston and a gear train for connecting said threaded shaft to said propeller for rotating the same about their respective axes upon rotation of said threaded shafts, said gear train including a ring gear embracing said hollow shaft at a location adjacent said cylinder and pinion gears carried by said threaded shafts and in engagement with said ring gear, and additional pinions engaging said ring gear and each connected through a shaft to one of said blades.

4. A variable pitch propeller mechanism in combination with a propeller hub having a plurality of propeller blades each rotatably anchored to said hub for angular movement about their respective axes, of means for biasing each of said bladeslabout its own axis comprising a cylinder having a piston therein With fluid on opposite sides thereof and actuated by the difference in pressure of the fluid on said piston, two conduits through which fluid flows to said cylinder, at plurality of pumps each supplying fluid under pres sure to said cylinder, one to one side of said piston and another to the other side of said piston",

a single manually operable valve for controlling the flow of fluid from said pumps, two by-pass conduits one from one of said conduits and the other in by-pass relation to the other ofsaid conduits, a governor actuated valve through which each of said by-pass conduits extend, an addi tional pump, a plurality of manually operable valves, conduits extending from said pumps to said valves, conduits from each of said valves to either side of said piston, and means actuated by the opening" of either of said valves foractuat ingsaid additional pump to force fluid under pressure through said conduits to a selected side ofsaid piston. r I j 5. A variable pitch propeller mechanism;. in

combination with a propeller hub having ;.a plu rality of propeller blades each rotatably anchored to said hub for angular movement about their respective axes, of means for biasing each of said blades about its own axis comprising a cylinder having a piston therein with fluid on opposite sides thereof, and actuated by the diiference in pressure of the fluid on said piston, two conduits through which fluid flows to said cylinder, S6133: rate sources supplying eachof said two conduits with fluid under pressure, one .to one side of said piston and the other to the other side of said piston, means to manually control the flow of fluid from said sources, an additional separate source of supply of fluid under pressure, a p111? rality of manually operable valves, conduits extending from said additional source of supply to said valves, conduits from each of said vaivesto either side of the piston one in reverse relation to the other whereby the selected valve will serve to move the piston in the desired direction- ROBERT STEVENSON. l 

